Production of silver mirrors by volatilisation



Unite States PRODUCTION OF SILVER MIRRORS BY VOLATILISATION No Drawing.Application October 29, 1953 Serial No. 389,156

Claims priority, application Netherlands November 15, 1952 3 Claims.(Cl. 117-35) It has been suggested before to provide a method ofproducing silver mirrors by silver-coating and rendering incandescent afilament made of a metal having a very high melting point, such astungsten or molybdenum. The article required to be coated with silver isthen placed near the filament.

This methods permits of providing, for example, glass bulbs for electricincandescent lamps or bowls for reflectors with a reflecting surface.

A known limitation consists in that silver wets the filament poorly andcontracts in drops so that the silver drops from the wire. It wassuggested before to add to the filament or to the silver a third metalapt to improve the adherence of the silver and to cause it to flow outabout the filament. It was suggested to use as the flux the metals ofthe eighth group and more particularly platinum, palladium, iridium,rhodium, iron, nickel and cobalt and also beryllium.

Even the use of these metals gives rise to difiiculties. It is true thatprecious metals, such as platinum have the desired effect, but theprecentage to be added to the silver is comparatively high. The bestresults are obtained with a silver alloy containing from 5 to 15% ofthese metals. However, such alloys are far more expensive than thesilver itself. Of the other metals a quantity of the order of 1% isadded to the silver. The adherence of such alloys is comparatively poorand it may be necessary previously to coat thefilament entirely withsuch an alloy by galvanic means.

According to the invention the flux used is silicon and this has theadvantage that minute quantities, in the order ent of 0.1%, aresufficient, the wetting of the filament being quite satisfactory. Inaddition, silicon satisfies the requirement that on volatisation it doesnot bring about any change in colour of the silver mirror.

For carrying out the method according to the invention pieces of asilver alloy containing for example 0.1% silicon may be introduced intoa filament of tungsten, molybdenum or similar high melting point metal.When glowing this alloy will spread quite evenly throughout the surfaceof the filament.

What is claimed is:

1. A method of producing silver mirrors comprising the steps,introducing an alloy of silver and a minute amount of silicon into ametallic filament consisting essentially of a refractory metal having ahigh melting point, and heating to incandescence said filament toevaporate the silver therefrom and deposit said silver on the surface ofa body placed in the vicinity of said filament thereby to form a silvemirror on said body.

2. A method of producing silver mirrors comprising the steps,introducing an alloy of silver and about 0.1% of silicon into a metallicfilament consisting essentially of a refractory metal having a highmelting point, and heating to incandescence said filament to evaporatethe silver therefrom and deposit said silver on the surface of a bodyplaced in the vicinity of said filament thereby to form a silver mirroron said body.

3. A method of producing silver mirrors comprising the steps,introducing an alloy of silver and about 0.1% of silicon into a metalicfilament consisting essentially of a refractory metal selected from thegroup consisting of tungsten and molybdenum, and heating toincandescence said filament to evaporate the silver therefrom anddeposit said silver on the surface of a body placed in the vicinity ofsaid filament thereby to form a silver mirror on said body.

References Cited in the file of this patent UNITED STATES PATENTS2,079,784 Williams May 11, 1937 2,138,637 Leach Nov. 29, 1938 2,386,876Ogle et al Oct. 16, 1945 2,424,085 Bergsteinsson July 15, 1947 2,450,340Hensel et al. Sept. 28, 1948 2,450,850 Colbert et al. Oct. 5, 19482,450,856 Colbert et a1. Oct. 5, 1948

1. A METHOD OF PRODUCING SILVER MIRRORS COMPRISING THE STEPS,INTRODUCING AN ALLOY OF SILVER AND A MINUTE AMOUNT OF SILICON INTO AMETALLIC FILAMENT CONSISTING ESSENTIALLY OF A REFRACTORY METAL HAVING AHIGH MELTING POINT, AND HEATING TO INCANDESCENCE SAID FILAMENT TOEVAPORATE THE SILVER THEREFROM AND DEPOSIT SAID SILVER ON THE SURFACE OFA BODY PLACED IN THE VICINITY OF SAID FILAMENT THEREBY TO FORM A SILVEMIRROR ON SAID BODY.